Use of alcohols as additives for plaster and/or mortar

ABSTRACT

Mortars and plasters containing additives which are alcohols having from 8 to 72 carbon atoms adsorbed on solid supports, and processes for the preparation of the additives.

FIELD OF THE INVENTION

This invention relates to the use of alcohols containing 8 to 72 carbonatoms per molecule as additives for plasters and/or mortars. Thealcohols are present in powder form, being adsorbed onto a solidsupport. This ensures that, besides other favorable properties, the opentime in particular of the corresponding mortars is extended.

BACKGROUND OF THE INVENTION

Mortars (cf. for example Gerhard Stehno: “Baustoffe undBaustoff-prüfung”, Springer Verlag, Vienna 1981, page 82) are understoodin the building industry to be mixtures of aggregates, binders and waterand, if desired, additives.

Plasters are different from mortars. Plasters are normally understood tobe mixtures of aggregates and binders and optionally additives.Accordingly, plasters are substantially “dry” systems. Plasters areconverted into mortars by stirring with water. In practice, plasters arenormally stirred with water, i.e. converted into mortars, just beforeuse.

The above-mentioned ingredients or functional components of plasters andthe mortars obtainable from them by adding water are as follows:

The so-called aggregates are generally mineral aggregates (sands) with amaximum particle size of 4 mm. The function of the sand is to form amineral framework in the mortar. By suitably selecting the sand, it ispossible favorably to influence both the volume stability and thestrength of the mortar. In most cases, natural sand is used, althoughartificial sands may also be used.

Binders are selected according to the required processability and therequired properties of the hardened mortar. By mixing the binder withwater, the individual aggregate particles are supposed to be coated andcemented together. In general, two types of binder are used. First,there are the mineral binders. Mineral binders are divided intoair-curing binders which cure exclusively in air after the addition ofwater, and hydraulic binders which can cure both in air and in waterafter the addition of water. Depending on the nature of the mineralbinder, the corresponding mortars are known as gypsum mortars, gypsumlime mortars, anhydrite mortars, anhydrite lime mortars, plaster andmasonry binding mortars, cement mortars and magnesia mortars. Besidesthe mineral binders mentioned, organic binders are also used. In theircase, the corresponding mortars are also known as synthetic resinmortars.

By incorporating additives, certain mortar properties, for examplepermeability to water, particularly good adhesion, workability, coloretc., can be influenced or improved.

Mortars can be classified in various ways. Typically, mortars areclassified according to

a) the type of binder used (for example cement mortar, lime mortar, limecement mortar, gypsum mortar, etc.),

b) the application envisaged (for example masonry mortars, plastermortars, Colgraut mortars, joint mortars, screed mortars, etc.) and

c) the hardening process (for example non-hydraulic mortars or hydraulicmortars).

The Following Observations Apply to Plaster Mortars:

Plasters are applied to walls and ceilings in one or more layers,according to requirements. Apart from the aesthetic appearance of thesurface, plasters provide protection against the effects of weather(external plasters) and form a smooth surface for screeds and wallpapers(internal plasters); in steel-reinforced concrete ceilings and stairsand in steel stanchions, they protect the steel cores against fire and,where porous aggregates are used, afford protection against heat.Basically, internal and external plasters should be able to breath, i.e.should allow the exchange of moisture by vapor diffusion between theplastered components and the atmosphere. Plaster mortars are used forplasters containing mineral binders while coating materials (syntheticresin plasters) are used for plasters containing organic binders. Bothcan act in combination as a plaster system. Coating materials for theproduction of synthetic resin plasters often consist of organic bindersin the form of dispersions or solutions and fillers in which most of theparticles are larger than 0.25 mm in size. They are normally supplied inprocessable form.

A general problem with plaster mortars is that they dry out prematurelyduring processing. To prevent such premature drying out (which resultsin crack formation, etc.), for example under the effect of air and/orsunlight, it is normally proposed in the relevant literature to protectplasters by suitable measures. These include spraying with water,sunscreening for external plasters, closing the window openings in thecase of internal plasters while allowing ventilation to evaporate themoisture (cf. Siefried Härig, Karl Günther, Dietmar Klausen,“Technologie der Baustoffe—Handbuch für Studium und Praxis”, Verlag C.F. Müller, Karlsruhe 1990, page 114).

In recent years, so-called dispersion plasters which containredispersible polymer powders as binders have acquired increasingsignificance. “Dispersion plasters” are so called because thecorresponding binders are prepared from aqueous polymer dispersionswhich have been converted into a dry state, for example by spray drying.If a plaster containing such a binder is contacted with water, thepolymers are redispersed, i.e. the mortar thus obtained now containspolymers as binder.

The increasing success of dispersion plasters is attributable inter aliato such advantages as better adhesion and elasticity and to theirwater-repellent character. However, in the plastering of relativelylarge surfaces, the open time of dispersion plasters is a criticalfactor, as already generally described above for plaster mortars. Thisis because, after drying accompanied by coalescence of the polymerdispersion, the resistance of the plaster to water reaches a first stageafter which the plaster can no longer readily be dissolved with water.The consequences are visible starting points. The problem is greater,the more heavily textured the plaster (rubbing plasters, textureplasters).

U.S. Pat. No. 3,486,916 describes cement mixtures characterized by adelayed free water release rate. These mixtures are obtained by addingan aqueous emulsion of C₁₄₋₂₀ fatty alcohols which form anevaporation-inhibiting film on the surface of the cast objects.

WO 95/04008 describes a dry cement with a reduced tendency to exude limeunder the influence of weathering, the hydraulic cement containing 0.01to 3% by weight of at least one C₁₄₋₂₂ fatty alcohol.

SU 950 703 (Derwent Abstract 63154 K/26) describes mixtures of variousfatty alcohols, hydrocarbons, soaps and fatty acid esters. Thesemixtures are used to protect the surface of freshly laid concreteagainst the over-rapid evaporation of water.

SU 652 154 (Derwent Abstract 88793 B/49) describes the pro-duction ofconcrete moldings. Freshly laid concrete is coated with a dilute aqueoussolution of cetyl alcohol. This is said to reduce the water evaporationrate by a factor of 4 to 5. The fatty alcohol layer is subsequentlyremoved.

DE-A-44 34 010 describes redispersible polymer powders containingamino-s-triazine/formaldehyde/sulfide condensates as effectiveprotective colloids which are of importance in the spray drying of thecorresponding polymer dispersions. According to page 3, lines 7 et seq.,the redispersible polymer powders contain vinyl- or acrylate-basedpolymers as their principal component. The examples of suitable polymersmentioned include products of vinyl acetate, vinyl propionate, vinyllaurate, vinyl chloride, vinylidene chloride, straight-chain or branchedvinyl esters containing 3 to 18 carbon atoms (versatates), acrylic andmethacrylic monomers, more especially esters, and styrene and ethenewhich may be present in the form of homopolymers, copolymers,terpolymers and as graft polymers.

DE-A-44 21 270 describes aqueous fatty alcohol dispersions which containC₁₀₋₂₈ fatty alcohols, anionic surface-active compounds and nonionicsurface-active compounds. The aqueous dispersions in question aresuitable as antifoam agents and as additives for dispersion-bondedplasters. According to page 5, lines 14 to 20, these aqueous fattyalcohol dispersions increase the open time of dispersion plasters. Inaddition, the tendency of dispersion plasters to develop cracks isdistinctly reduced where these dispersions are used. A reduction inwater absorption and hence an increase in the hydrophobicizing effect ofthe plasters are further advantages. Finally, the plasters also lendthemselves to coating and have high permeability to water vapor.However, DE-A-44 21 270 discloses only aqueous dispersions containinginter alia fatty alcohols to increase the open time of dispersionplasters. Accordingly, DE-A-22 21 270 discloses fatty alcohols indispersion form as open time extenders for dispersion plasters which arepackaged as water-containing pastes.

SUMMARY OF THE INVENTION

The problem addressed by the present invention was to provide additivesfor plasters and/or mortars which would ensure that the mortarscontaining these additives, which are obtainable either

by stirring the plasters containing the additives with water or

by stirring the individual components (aggregates, binders andadditives) with water,

would be distinguished by an increase in their open time.

The problem stated above has been solved by special additives. Theseadditives are alcohols in powder form, the alcohols which are adsorbedonto a solid support containing 8 to 72 carbon atoms per molecule andbeing branched or unbranched, saturated or unsaturated.

In the context of the invention, the term “alcohols” is understood toapply both to individual alcohols with a defined chain length and tomixtures of alcohols in the C-chain length range mentioned.

In the context of the present invention, the expression “powder form” isunderstood to mean that the alcohols, i.e. the solid supports coatedwith the alcohols, are present in a pourable or free-flowing powderform. It does not matter whether the powder feels slightly moist or not.

The additives according to the invention afford the followingadvantages: the drying time of the mortar system is extended. In thisway, rubbing plasters can be textured even after a relatively longdrying time and differences in the plaster textures—rubbed off atdifferent times—are minimized. In addition, the so-called“water-repellent effect” characteristic of other commercially availablehydrophobicizing agents does not occur where the additives according tothe invention are used. However, the additives are capable of increasingthe time which water coming from outside takes to penetrate. It has alsobeen found that the use of the additives according to the invention doesnot cause any coating adhesion problems. Finally, the additivesaccording to the invention distinctly reduce the tendency towards crackformation. Another advantage of using the additives according to theinvention is that plaster systems prepared with them are flexible andcan be applied and spread with little effort.

Disadvantages, such as accelerated cement reaction and reducedresistance (early water, UV, etc.), are not in evidence.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a first embodiment, the present invention relates to the use ofalcohols as additives for plasters and/or mortars. The additives arepresent in powder form, the alcohols being adsorbed onto a solidsupport. The chain length of the alcohols is in the range from 8 to 72carbon atoms per molecule. As already mentioned, the alcohols may besaturated or unsaturated, linear or branched. In addition, they may beused either as individual species or in the form of mixtures with oneanother.

Basically, the choice of the solid support is not critical. However, asolid support to be used in accordance with the invention should becapable of optimally absorbing an aqueous alcohol dispersion so that, onthe one hand, the water present is largely bound internally, leaving theoutside substantially dry, and on the other hand the alcohols areadsorbed onto the surface and/or in zones near the surface. In preferredembodiments, therefore, the solid support should be porous and, inparticular, should have medium to good porosity. In common usage,porosity is understood to be the property of the solid support to beprovided with pores. Porous materials are often characterized by the socalled pore volume. In this regard, the choice of a certain pore volumefor porous solid supports is basically not critical. Accordingly, it ispossible to use both supports with coarse pores and supports with finepores (macropores, mesopores or micropores).

The use of porous materials as the support provides for an increase inthe surface of the particles of the solid support and, hence, for a highadsorption capacity for the alcohols to be used in accordance with theinvention. It follows from the various requirements mentioned thatpreferred solid supports are selected from the group of solidadsorbents. By definition, adsorbents are substances which, by virtue oftheir large surface, are capable of selectively concentrating certainsubstances at their surface to an extent which is greater, the morefinely divided the adsorbent. Accordingly, porous substances aregenerally good adsorbents, as well-known to the expert.

Examples of suitable supports are silicas, silica gels (includingmolecular silica gels, colloidal or unformed silica of elastic to solidconsistency with a loose to compact pore structure—silica being presentin the form of highly condensed polysilicic acids), aluminium oxides,aluminium silicates, kaolin, chalk, microtalcum, barium sulfate,titanium white, zeolites and the like. According to the invention,particularly preferred supports are silicas, especially precipitatedsilicas.

In principle, the alcohols may be applied to the solid supports invarious ways. For example, the alcohols may be applied to the solidsupport in liquid or molten form or may be sprayed onto the support.However, they may also be applied in the form of an aqueous dispersion.According to the invention, the production of the alcohols in powderform is preferred and is described hereinafter. The advantage is that,where supports of medium to high porosity, i.e. supports with anincreased surface, are used, considerably more alcohol can be adsorbedonto the surfaces or into zones near the surface although, on the otherhand, the water emanating from the alcohol dispersion can be effectivelybound by the support.

The solid supports to be used for the production of the additivesaccording to the invention are powder-form, pourable or free-flowingmaterials. Basically, the particle size of the support is not critical.Where the supports are used in mortars, however, at least 80% of theparticles are preferably smaller than 1 mm in diameter. The diameter ofat least 80% of the particles is preferably smaller than 1 mm, most ofthe remaining particles having a mean particle diameter of 1 to 3 mm.The morphology or shape of the particles is not a critical factor. Theparticles may be both spherical, rodlet-shaped or even amorphous. Theparticle size distribution may readily be determined by shaking aweighed Quantity of a powder-form solid support through a sieve with adefined mesh width (for example 1 or 3 mm) and determining thepercentage of material retained by the sieve by differential weighing.

As already mentioned, the alcohols present in the additives according tothe invention may be present as individual species or in the form ofmixtures with one another. The alcohols may be saturated or unsaturated,linear or branched. Examples of particularly suitable classes ofalcohols are fatty alcohols of natural origin containing 8 to 24 carbonatoms per molecule, derivatives of fatty alcohols, such as Guerbetalcohols and dimer and/or trimer alcohols, and finally oxoalcohols.

A preferred embodiment of the present invention is characterized by theuse of fatty alcohols, preferably mixtures of fatty alcohols of naturalorigin. These mixtures may contain saturated and/or unsaturated fattyalcohols. Examples of suitable fatty alcohols are caprylic alcohol,pelargonic alcohol, capric alcohol, 1-undecanol, lauryl alcohol,1-tridecanal, myristyl alcohol, 1-pentadecanol, palmitoleyl alcohol,1-heptadecanol, stearyl alcohol, 1-nonadecanol, arachidyl alcohol,1-heneicosanol, behenyl alcohol, 1-tricosanol, lignoceryl alcohol, oleylalcohol, elaidyl alcohol, ricinoleyl alcohol, linoleyl alcohol,linolenyl alcohol, gadoleyl alcohol, arachidonyl alcohol, erucyl alcoholand brassidyl alcohol.

In another embodiment, Guerbet alcohols are used. Guerbet alcohols arecompounds corresponding to general formula (I):

R¹—CH(CH₂OH)—R²  (I)

in which R¹ and R² independently of one another represent an alkyl groupcontaining 6 to 12 carbon atoms, with the proviso that the total numberof carbon atoms per molecule is in the range from 16 to 24. The Guerbetalcohols (I) are produced by synthesis methods known per se in organicchemistry. In addition, many Guerbet alcohols are commerciallyavailable.

In another embodiment, dimer and/or trimer alcohols are used. Dimer andtrimer alcohols are alcohols which are derived from so-called dimer andtrimer fatty acids by replacement of the COOH function by an OHfunction. Dimer fatty acids are known among experts to be carboxylicacids which can be obtained by oligomerization of unsaturated carboxylicacids, generally fatty acid mixtures, such as oleic acid, linoleic acid,erucic acid and the like. The oligomerization is normally carried out atelevated temperature in the presence of a catalyst, for example of clay.The products obtained are mixtures of various substances, thedimerization products predominating. However, certain percentages ofhigher oligomers, more particularly trimer fatty acids, are alsopresent. In addition, trimer fatty acids also contain monomers ormonobasic carboxylic acids from their production. Dimer fatty acids arecommercially available products and are marketed in various compositionsand qualities. According to the invention, it is preferred to use dimerdiols emanating from dimer fatty acids which have a dimer content of atleast 50% and preferably of at least 75% and in which the number ofcarbon atoms per dimer molecule is predominantly in the range from 36 to44. Similarly to the dimer fatty acids, the trimer fatty acids are alsooligomerization products of unsaturated fatty acids in which thepercentage of trimers in the product predominates. Trimer fatty acidsare also commercially available products. Dimer diols and trimer triols,which represent possible alcohols to be used in accordance with theinvention, may be obtained for example by hydrogenation of dimer andtrimer fatty acids. The hydrogenation reaction is normally carried outin the presence of copper- and/or zinc-containing catalysts in standardcontinuous pressure hydrogenation reactors with gas circulation.

In another embodiment, oxoalcohols are used. Oxoalcohols aresynthetically produced alcohols. These alcohols, which are obtained inthe so-called oxosynthesis, are mostly primary and branched. Examples ofcommercially available oxoalcohols are isooctyl, isononyl, isodecyl andisotridecyl alcohol.

The powder form of the alcohols is preferably produced by contacting asolid—and preferably porous—support with an aqueous dispersion of thealcohols and mixing the support and dispersion in mixers of the typetypically used for producing powders.

Accordingly, the present invention also relates to a process for theproduction of alcohols in powder form which is characterized in that asolid support is contacted with an aqueous dispersion of alcoholscontaining 8 to 72 carbon atoms per molecule and the support anddispersion are mixed in mixers of the type typically used for producingpowders, for example in a Lödige mixer. The aqueous alcohol dispersionsused preferably have an alcohol content of 5 to 50% by weight, based onthe dispersion as a whole. An alcohol content of 15 to 35% by weight isparticularly preferred. The ratio by weight of alcohol dispersion tosupport is preferably adjusted to a value of 20:80 to 80:20. A ratio byweight of alcohol dispersion to support of about 70:30 is mostparticularly preferred.

The additives according to the invention on the one hand may be mixedwith aggregates and binders to form ready-to-use plasters which areconverted into the corresponding mortar by stirring with waterimmediately before use. On the other hand, the additives may beseparately stored and only used immediately before preparation of themortar.

For practical reasons, the first of these two alternatives is the moreimportant. To prepare mortars from such plasters containing theadditives according to the invention, the plasters are stirred withwater and then left to ripen for a few minutes.

Accordingly, the present invention also relates to plasters containingaggregates, binders and additives which are characterized in that theadditives are alcohols in powder form which are adsorbed onto a solidsupport, the alcohols containing from 8 to 72 carbon atoms per molecule,and to mortars obtainable by stirring the plasters with water.

In one preferred embodiment, the plasters contain the additivesaccording to the invention in quantities of 0.01 to 10% by weight, basedon the plaster as a whole. Quantities of 0.3 to 2% by weight areparticularly preferred.

There are no restrictions on the aggregates and binders which may beused in the plasters and mortars according to the invention.Accordingly, any of the usual materials well-known to the expert may beused. Examples can be found in the preamble to the description under theheading “Prior Art”. If desired, other typical additives besides theadditives according to the invention may be added to the plasters ormortars.

The following Examples are intended to illustrate the invention withoutlimiting in any way.

EXAMPLES

1. Production of an Additive According to the Invention

An aqueous dispersion of a mixture of natural fatty alcohols (“Loxanol842 DP/6”; C-chain range 14-20; concentration of the fatty alcohols inthe dispersions: 20% by weight; a product of Henkel KGAA, Düosseldorf)was mixed with silica (“Sipernat 22 S”; fine-particle, spray-dried andground silica; manufacturer: Degussa AG, Frankfurt am Main) in a ratioby weight of 70:30 in a typical laboratory mixer for producing powders(Multi-Mix, Type MX 31). To this end, the silica was introduced firstand the aqueous dispersion of the mixture of natural fatty alcohols wasthen added while stirring at the lowest speed setting and the whole wasintensively stirred for about 20 to 30 seconds (medium stirring speed).The additive obtained in this way is referred to hereinafter as A-1.

Other silicas were similarly used as supports. The additive producedwith silica FK 310 is referred to as A-2 and the additive produced withsilica FK 320 as A-3. The additive produced with Sipernat 50 is referredto as A-4 and the additive produced with Sipernat 50 S as A-5.

Particulars of the silicas mentioned in the last paragraph can be foundin the company publication “Fällungskieselsäuren undSilikate-Herstellung, Eigenschaften und Anwendungen (PrecipitatedSilicas and Silicates—Production, Properties and Uses)”; Degussa AG,Frankfurt am Main, Germany: Kiselsäure FK 310: very fine-particle silicawith a BET surface of 650 m²/g; Kiselsäure FK 320: silica; Sipernat 50:spray-dried carrier silica with particularly high absorbency; Sipernat50 S: obtained by grinding Sipernat 50 and thus of relatively smallparticle fineness.

2. Formulation of an Organosilcate Powder Plaster

A formulation containing an open time extender according to theinvention (additive A-1) is shown by way of example in the followingTable. Several performance tests were carried out on the basis of and inaccordance with this formulation (cf. point 3).

Parts by Component weight Function Manufacturer Portil K 5.40 WaterglassHenkel KGaA HYDROPALAT 0.30 Wetting agent (flow Henkel KGaA 760 aid)Mowilith LDM 4.20 Dispersion Hoescht AG 2072 P TEXAPON 0.12Air-entraining agent Henkel KGaA K12-96 Zilosil 16 1.20 Film formingagent Omya GmbH Tylose H 15000 0.25 Thickener Hoescht AG YP2 FOAMASTER0.70 Powder defoamer Henkel KGaA PD-1 Arbocel B 400 c 1.20 FiberRettenmeier & Söhne Bayertitan RFDI 7.00 Pigment Bayer AG Omyacarb 10 GU7.00 Filler Omya GmbH Omyacarb 40 GU 13.10 Filler Omya GmbH Omyacarb 1308.38 Filler Omya GmbH GU Aluminiumoxid 1.00 Filler Martinswerk PS-6Plastorit 4.00 Filler Naintsch Mineral- Naintsch 0.5 werke Calcilit1.8-2.5 45.15 Filler Alpha Calcit KA Füllstoffe Additiv A-1 1.00 Opentime extender

Manufacturers:

Henkel KGaA (Düsseldorf, Germany), Hoechst AG (Frankfurt, Germany), OmyaGmbH (Cologne, Germany), Rettenmeier & Söhne (Ellwangen, Germany), BayerAG (Leverkusen, Germany), Martinswerk (Bergheim, Germany), NaintschMineralwerk GmbH (Graz, Austria), Alpha Calcit Füllstoffe (Cologne,Germany).

3. Performance Tests

3.1. Open Time

The organosilicate powder plaster described in 2. was stirred with waterto form a mortar. 23 Parts by weight of mixing water were added to 100parts by weight of the above formulation and the mortar was allowed toripen for 5 minutes after stirring. The mortar was then applied to aglass plate in a defined layer thickness. A needle (made of stainlesssteel, length 20 mm, diameter 1 mm) was then inserted into the wetcoating material. The force which the needle required to move throughthe wet film at a defined speed (21.8 cm/h) was then measured. Theresults were recorded on a recorder.

This method is based on the principle whereby a lower force is requiredand hence recorded in the first (time) phase after application of themortar to the glass plate. However, when the drying time begins, theforce required increases considerably. The corresponding measuringpoints correlate exactly with the open time of the mortar used.

An open time of 27 minutes was measured for the mortar prepared as justdescribed on the basis of the formulation described in 2. (as described,the organosilicate powder plaster contained 1.0 part by weight ofadditive A-1 according to the invention). By comparison, an open time ofonly 12 minutes was measured for a mortar which had also been preparedon the basis of the organosilicate powder plaster described in 2., butwithout an additive according to the invention. By increasing the amountof additive A-1 according to the invention in the powder plasterformulation mentioned, the open time was extended to as long as 32minutes.

3.2. Crack Formation

After processing, the mortar based on the organosilicate powder plastercontaining 1.0% by weight of additive A-1 (and a corresponding mortarwith half the content of additive A-1 according to the invention) showedno cracks. By contrast, the corresponding mortar without additive A-1according to the invention showed slight but clearly visible crackformation.

3.3. Hydrophobicization

Drops of water colored with methylene blue were applied by pipette to apaint film. The time the water took to penetrate into the film was thenmeasured. In the case of the sample prepared on the basis of the mortarwhich did not contain additive A-1 according to the invention, the waterpenetrated directly into the film. The water penetrated through to thesubstrate, i.e. to the glass plate. By contrast, in the case of thesamples prepared on the basis of the formulation containing additive A-1according to the invention, the water spread over the surface of thefilm. Accordingly, the penetration time was increased and the depth ofpenetration reduced. The penetration time was 5 seconds in the case ofthe sample without A-1 and between 60 and 135 seconds in the case of theA-1-containing samples (depending on the concentration of the additiveA-1). The corresponding concentration range of additive A-1 in theorganosilicate powder plaster on which the mortar was based was in therange from 0.5 to 2.0% by weight.

3.4. Other Additives

The advantages of using additive A-1, as described in 3.1 to 3.3, werealso observed where additives A-2 to A-5 according to the invention wereused.

What is claimed is:
 1. In a plaster or mortar, the improvement whereinthe plaster or mortar contains an open time-enhancing quantity of anadditive in powder form comprising a solid support onto which isadsorbed at least one alcohol having from 8 to 72 carbon atoms, whereinthe solid support is at least one support selected from the groupconsisting of silicas, silica gels, aluminum oxides, aluminum silicates,kaolin, chalk, microtalcum, barium sulfate, titanium white, andzeolites.
 2. The plaster or mortar of claim 1 wherein the solid supportis silica.
 3. The plaster or mortar of claim 2 wherein the silica isprecipitated silica.
 4. The plaster or mortar of claim 1, wherein thealcohol is at least one alcohol selected from the group consisting of afatty alcohol containing from 8 to 24 carbon atoms, a Guerbet alcoholcontaining from 16 to 24 carbon atoms, a dimer alcohol, a trimeralcohol, and an oxoalcohol.
 5. The plaster or mortar of claim 1 whereinthe particle size of the solid support is such that at least about 80%of the particles are smaller than 1 mm in diameter.
 6. The plaster ormortar of claim 1 wherein the at least one alcohol is at least one fattyalcohol.
 7. The plaster or mortar of claim 6 wherein the at least onefatty alcohol is a mixture of fatty alcohols of natural origin.
 8. Theplaster or mortar of claim 6 wherein the alcohol is a Guerbet alcohol ofthe formula R¹—CH(CH₂OH)—R² wherein R¹ and R² independently represent aC₆₋₁₂ alkyl group, with the proviso that the total number of carbonatoms is from 16 to
 24. 9. The plaster or mortar of claim 4 wherein thealcohol is a dimer alcohol mixture having a dimer content of at leastabout 75% and contains predominantly dimer alcohols having from 36 to 44carbon atoms.
 10. The plaster or mortar of claim 1 wherein the additiveis made by contacting the solid support with an aqueous dispersion ofthe at least one alcohol.
 11. The plaster or mortar of claim 10 whereinthe aqueous dispersion contains from about 5 to about 50% by weight ofalcohol.
 12. The plaster or mortar of claim 10 wherein the ratio byweight of alcohol dispersion to solid support is from about 20:80 toabout 80:20.
 13. A process for the preparation of alcohols in powderform comprising the steps of A) contacting a porous solid support withan aqueous dispersion of at least one alcohol containing from 8 to 72carbon atoms; and B) mixing the porous solid support and the aqueousdispersion to produce a powder; wherein the alcohol is adsorbed onto theporous solid support, and the water in the aqueous dispersion is boundby the porous solid support; wherein the porous solid support is atleast one porous solid support selected from the group consisting ofsilicas, silica gels, aluminum oxides, aluminum silicates, kaolin,chalk, microtalcum, barium sulfate, titanium white, and zeolites; andwherein the at least one alcohol is selected from the group consistingof fatty alcohols, Guerbet alcohols, dimer alcohols, trimer alcohols,and oxoalcohols.
 14. The process of claim 13 wherein the aqueousdispersion has an alcohol content of from about 5 to about 50% by weightbased on the weight of the dispersion.
 15. The process of claim 13wherein the ratio by weight of aqueous dispersion to solid support is inthe range of from 20:80 to 80:20.
 16. The process of claim 15 whereinsaid ratio is about 70:30.
 17. A plaster comprising a) at least oneaggragate; b) at least one binder; and c) an open time-enhancingquantity of an additive in powder form comprising a solid support ontowhich is adsorbed at least one alcohol having from 8 to 72 carbon atoms,wherein the solid support is at least one support selected from thegroup consisting of silicas, silica gels, aluminum oxides, aluminumsilicates, kaolin, chalk, microtalcum, barium sulfate, titanium white,and zeolites.
 18. The plaster of claim 17 wherein component c) ispresent in from about 0.3 to about 2.0% by weight, based on the weightof the plaster.
 19. The plaster of claim 17 wherein the solid support issilica.
 20. The plaster of claim 19 wherein the silica is precipitatedsilica.
 21. The plaster of claim 17 wherein the alcohol is at least onealcohol selected from the group consisting of a fatty alcohol containingfrom 8 to 24 carbon atoms, a Guerbet alcohol containing from 16 to 24carbon atoms, a dimer alcohol, a trimer alcohol, and an oxoalcohol. 22.The plaster of claim 17 wherein the particle size of the solid supportis such that at least about 80% of the particles are smaller than 1 mmin diameter.
 23. The plaster of claim 17 wherein the at least onealcohol is at least one fatty alcohol.
 24. The plaster of claim 23wherein the at least one fatty alcohol is a mixture of fatty alcohols ofnatural origin.
 25. The plaster of claim 17 wherein the alcohol is aGuerbet alcohol of the formula R¹—CH(CH₂OH)—R² wherein R¹ and R²independently represent a C₆₋₁₂ alkyl group, with the proviso that thetotal number of carbon atoms is from 16 to
 24. 26. The plaster of claim17 wherein the alcohol is a dimer alcohol mixture having a dimer contentof at least about 75% and containing predominantly dimer alcohols havingfrom 36 to 44 carbon atoms.
 27. The plaster of claim 17 wherein theadditive is made by contacting the solid support with an aqueousdispersion of the at least one alcohol.
 28. The plaster of claim 27wherein the aqueous dispersion contains from about 5 to about 50% byweight of alcohol.
 29. The plaster of claim 27 wherein the ratio byweight of alcohol dispersion to solid support is from about 20:80 toabout 80:20.
 30. A mortar obtained by mixing the plaster of claim 17with water.